Liverpool ended Napoli's unbeaten run of 21 games on Tuesday, but their 2-0 victory was insufficient to knock the Italians out of first place in Champions League Group A.
Both teams had already been assured of a place in the last 16, but Jurgen Klopp's men shrugged off their Premier League woes on a European night at Anfield.
After Alex Meret narrowly saved Darwin Nunez's header five minutes from time, Mohamed Salah forced the ball over the line.
Nunez then added a second with the game's final kick to give Liverpool their fifth Champions League victory since falling 4-1 to Napoli in September.
Because of the comprehensive margin of victory, Luciano Spalletti's side only needed to avoid defeat by a four-goal margin to secure first place.
"I had the impression my team was slowing down because we knew we had that margin," said Spalletti.
The Reds were defeated 2-1 by Leeds at home in the Premier League in front of a crowd for the first time in over five years on Saturday.
However, another lengthy VAR review revealed Nunez was on board, allowing both he and Van Dijk to laugh.